The invention relates to an electrical connector for transmitting high speed electronic signals, and more particularly, to an electrical connector having signal contacts opposing a ground contact to provide signal transmission lines of controlled characteristic impedance and low cross talk.
Electronic devices that operate, in part, to send electronic signals and to receive electronic signals communicate with one another by way of the electronic signals that are transmitted over signal transmission lines provided by a transmission line device, for example, a circuit board or an electrical cable. New electronic devices continue to be developed, which transmit the signals at ever increasing speed, and which devices simultaneously process increased numbers of simultaneously occurring signals. Further, these new electronic devices benefit from miniaturization, which increases the number of circuits for processing signals simultaneously, and which significantly reduces signal transmission delays, as the electronic devices become more miniaturized.
The signal transmission lines, which connect with the electronic devices that communicate with one another, transmit multiple high-speed signals with minimized signal distortion. Further, the signal transmission lines, as well as associated electrical connectors that connect with the transmission lines, are of controlled characteristic impedance that matches the characteristic impedance of the electronic devices to which the transmission lines are connected. The electrical connectors of matched characteristic impedance are also known as matched impedance electrical connectors. The signal transmission lines and the electrical connectors benefit from miniaturization, similarly as do the electronic devices.
A known electrical connector of the matched impedance type has signal contacts provided with electrical terminals for making electrical connections with signal transmission lines on a transmission line device, such as circuit traces on a circuit board or electrical conductors of an electrical cable. Further, the known electrical connector has a single broad, conducting ground contact with multiple tails. The signal contacts are arranged to oppose the ground contact, which provides signal transmission lines of controlled characteristic impedance. For example, an embodiment of the known electrical connector is disclosed by U.S. Pat. No. 5,114,355, and has an insulating housing that urges both a ground contact and an entire contact row of signal contacts against an intervening wall on the housing, which minimizes variations in characteristic impedance along the lengths of the signal contacts.
The characteristic impedance is determined by mathematical analysis of each signal transmission line of the electrical connector. The mathematical analysis emulates the well-known mathematical analysis of a microstrip type of transmission line to determine its characteristic impedance. The characteristic impedance of a signal transmission line of an electrical connector is determined, partly by a ratio, of the width of a signal contact versus the thickness of each of the dielectric materials separating the signal contact from the opposed ground contact, and partly by the permittivity and other properties of such dielectric materials, which influence propagation of a signal in the respective dielectric materials. Such dielectric materials for an electrical connector assembly may include the insulation material of the housing. Further, such dielectric materials may include ambient air, for example, as disclosed by U.S. Pat. No. 5,046,960, wherein an embodiment of the known electrical connector is purposely provided with air reservoirs of controlled widths, as determined by analytical methods, on both sides of a ground bus, which assist in controlling characteristic impedance.
The known electrical connector may include signal contacts that are arranged in pairs. Each pair of signal contacts opposes a ground contact to provide a signal transmission line pair of controlled characteristic impedance. A signal transmission line pair is desirable in an electrical connector for transmitting differential pair signals. Differential pair signals are ideally, two simultaneous signals of equal signal strength and of opposite polarity. The signal contacts of each signal transmission line pair transmit the differential pair signals. Any cross talk influences as between the signal contacts of the same pair effectively cancel, because such cross talk influences occur simultaneously and are of opposite polarity. However, in the known electrical connector, consecutive signal transmission line pairs are provided by having the pairs of signal contacts arranged consecutively in the same contact row, which means that cross talk between such consecutive pairs of signal contacts may exceed acceptable levels. Specifically, as such pairs of contacts transmit high-speed signals, undesired levels of cross talk are induced in another pair of consecutively arranged signal contacts. The levels of cross talk can be reduced to acceptable levels by spacing consecutive pairs of contacts sufficiently far apart from one another in the same contact row. However, spacing the pairs of contacts far apart increases the length of the contact row and prevents desired miniaturization of the electrical connector. Accordingly, a need exists for an electrical connector having signal transmission line pairs that avoid consecutively arranged pairs of signal contacts.
Another embodiment of the known electrical connector is disclosed by U.S. Pat. No. 4,975,084, and has pairs of signal contacts arranged consecutively in a column. The column is essentially a contact row that extends transversely of the length of the known electrical connector, instead of a contact row that extends lengthwise of the known electrical connector. Because the pairs of signal contacts are arranged consecutively in the contact row, they contribute to unacceptable levels of cross talk. Consecutive pairs of signal contacts have the same disadvantages, whether the consecutive pairs are in a contact row that extends lengthwise of an electrical connector, or whether the consecutive pairs are in a contact row that extends transversely, as a column.
Further, having consecutive pairs of signal contacts arranged close together, means that pairs of signal terminals on the pairs of signal contacts are arranged close together, and provide an inadequate space surrounding the pairs of signal terminals for limiting cross talk to acceptable levels.
Another disadvantage stems from having the pairs of signal contacts arranged consecutively in a contact row. The pairs of signal contacts have corresponding pairs of signal terminals thereon for making electrical connections to signal transmission lines on a transmission line device, such as signal transmission lines on a circuit board, or electrical conductors of an electrical cable. As consecutive pairs of signal contacts become more closely spaced together to achieve miniaturization of the known electrical connector, the corresponding pairs of signal terminals become more crowded together, which means there is insufficient space surrounding the consecutive pairs of signal terminals within which to route signal transmission lines, and within which to provide terminal connection areas, also known as pads, to which the signal and ground terminals are connected.
In each embodiment of the known electrical connector, the ground contact serves as a ground bus for an entire contact row of consecutive signal contacts. One disadvantage is that signals being transmitted by such contacts increase inductance in the ground contact. In response to minimizing this disadvantage, another embodiment of the known electrical connector, referred to as a connector half by U.S. Pat. No. 4,762,500, has a ground bus that is provided with multiple tails for connection to ground or reference electrical potential to minimize ground bus inductance. The tails are also known as ground terminals. However, increasing the number of ground terminals means that the ground terminals become crowded, and there is insufficient space surrounding the ground terminals within which to route signal transmission lines, and within which to provide terminal connection areas, or pads, to which the ground terminals are connected.
Accordingly, an object of the invention is to satisfy an existing need for an electrical connector, which has consecutive pairs of signal transmission lines of controlled characteristic impedance, and which eliminates consecutive pairs of signal contacts in the same contact row to minimize levels of cross talk.
Another object of the invention is to satisfy an existing need for an electrical connector having consecutive pairs of signal transmission lines of controlled characteristic impedance as provided by pairs of signal contacts opposing ground contacts, and yet provide adequate spaces surrounding pairs of signal terminals on the signal contacts for reducing cross talk and for providing connection pads and for routing signal transmission lines.
Another object of the invention is to satisfy an existing need for an electrical connector having consecutive pairs of signal transmission lines, and the connector minimizes the number of ground terminals on a ground contact, which reduces crowding of the of the ground terminals, and provides adequate spaces surrounding the ground terminals within which to provide terminal connection areas, or pads, and within which to route signal transmission lines.
The invention includes an electrical connector having consecutive signal transmission line pairs. Each signal transmission line pair has a pair of signal contacts in one contact row opposing a ground contact in another contact row. A ground contact of a consecutive signal transmission line pair faces in a reverse direction from the one faced by a ground contact of a previous signal transmission line pair. A ground contact of the consecutive signal transmission line pair is in the same contact row as is a pair of signal contacts of the previous signal transmission line pair, such that, each consecutive signal transmission line pair faces in a reverse direction from the one faced by a previous signal transmission line pair. The electrical connector minimizes cross talk between different pairs of signal contacts by having consecutive signal transmission line pairs facing in reverse directions, which avoids an arrangement of consecutive pairs of signal contacts in the same contact row, as was provided by prior, known electrical connectors.
According to a further feature of the invention, an electrical connector has consecutive signal transmission line pairs. Each signal transmission line pair has a pair of signal contacts in one contact row opposing a ground contact in another contact row. A ground contact of a consecutive signal transmission line pair is in the same contact row as is a pair of signal contacts of a previous signal transmission line pair. The pair of contacts of the previous signal transmission line pair has a corresponding previously arranged pair of signal terminals extending to one terminal row. The pair of signal contacts of the consecutive signal transmission line pair has a corresponding consecutively arranged pair of signal terminals extending to another terminal row. The ground contacts of both the consecutive signal transmission line pair and the previous signal transmission line pair have respective single ground terminals extending to an intervening terminal row that is between said one terminal row and said another terminal row. Advantageously, the ground terminals extending to the intervening terminal row serve to intervene between the consecutively arranged pair of signal terminals and the previously arranged pair of signal terminals, which minimizes cross talk influences between the consecutively arranged pair of signal terminals and the previously arranged pair of signal terminals. Further, advantageously, respective ground contacts have respective single ground terminals, which reduces the number of terminals on each of the ground contacts.
According to another feature of the invention, each signal transmission line pair has a group of terminals that is provided by a single ground terminal on a corresponding ground contact and a pair of signal terminals on a corresponding pair of signal contacts, and each pair of signal terminals extend along centerlines that are closer together than are the centerlines of the corresponding pair of signal contacts, which minimizes a space between each pair of signal terminals, and which maximizes a space surrounding each group of terminals for routing signal transmission lines on a transmission line device to which the group of terminals is to be connected. Further, the respective laterally offset portions situate the respective pair of signal terminals relatively close together, thereby decreasing a space between the pair of respective signal terminals and increasing a cross talk reducing space surrounding the pair of respective signal terminals.
According to another feature of the invention, each signal transmission line pair has a pair of signal terminals and a single ground terminal arranged in a group of terminals, the pair of signal terminals are on a corresponding pair of signal contacts, the single ground terminal is on a corresponding ground contact that is spaced at a distance from the pair of signal contacts, and the single ground terminal extends along a centerline that is closer to the pair of signal terminals than the distance between the ground contact and the pair of signal contacts, which minimizes a space between the ground contact and the pair of signal terminals, and which maximizes a space surrounding the group of terminals for routing signal transmission lines on a transmission line device to which the group of terminals is to be connected.
According to a further feature of the invention, each signal transmission line pair has a pair of signal terminals and a single ground terminal arranged in a group of terminals, the signal terminals of each signal transmission line pair extend along centerlines that intersect corners of a base of a triangular area for the signal transmission line pair, the ground terminal of each signal transmission line pair extends along a centerline that intersects an apex of the triangular area, and the triangular area for a consecutive signal transmission line pair is inverted with respect to a triangular area for a previous signal transmission line pair, which arranges the pairs of signal terminals of the consecutive and previous signal transmission line pairs a maximized distance apart to minimize cross talk influences therebetween.
Other objects and advantages of the invention will become apparent from the following description taken in conjunction with accompanying drawings.